In general this invention relates to electric heating and in particular to auxiliary heating for an internal combustion engine vehicle coolant flow system which includes a radiator element for transferring heat contained in the coolant to an enclosed area.
Cold weather start up of internal combustion engine vehicles has carried with it numerous costs and inconvenience. The passenger compartment is an uncomfortable, chilly enclosure when at ambient temperature, and the windows are frosted. The cold engine is hard to start because oil is thick and friction is high. When the engine is started, the friction takes its toll in wear on the parts. During the warm up period, fuel expenditures is higher, whether just idling or driving. These problems are inherent to gasoline and diesel engine type vehicles. Diesel engines, are tougher to start than gasoline engines and an operator of a large diesel truck often will leave the motor running for hours at rest stops and during long waits at delivery depots rather than chance difficult restart of a cold engine.
The majority of the passenger cars are left on the street over night. Those that are garaged escape obtaining frosted windows but little else, for a heated garage is a luxury few care to pay for. It is more efficient to heat relevant portions of the vehicle rather than its surrounding environment, and many ways to obtain that effect have been propounded over the last 70 or so years. The most common apparatus described for that purpose is an electric heater which heats engine coolant or its oil by conduction and convection. For example it may be installed in a hose section which is, in turn, interposed in the lower radiator hose between the engine and the radiator used for cooling the engine. Such a device is announced by J. C. Whitney & Co.; 1917-19 Archer Avenue, Chicago, IL, 60680, in the 1983 catalog (item 55-2528B, pg. 8). Similar devices are described in U.S. Pat. No. 1,683,920 issued to J. E. Rohne on Sept. 11, 1928 and in U.S. Pat. No. 1,267,416 issued to T. H. Jacob on May 28, 1918. Rhone has the heating element outside the hose section and Jacob has it located within the section.
Other conduction and convection type devices include clamp-type heaters which attach directly to an engine block (J. C. Whitney item 54-1171T, pg. 7), and freeze plug engine heaters which replace the freeze plug on the side of the block. (item 55-2363U, pg. 8). The above devices provide heat primarily to the vehicle's engine and not to the enclosed area of the vehicle comprising the passenger and cargo areas.
Installing an electric heating element in the vehicle's heater radiator and turning on its blower fan prior to use by the driver is described in U.S. Pat. No. 2,819,373 issued Jan. 7, 1958 to Roy D. Allman. His device warms the vehicle's enclosed area only, prior to entry by the driver. A heater with a pump for installation in the heater return hose is presently available (Whitney; item 54-1262P, pg. 7). This device warms the engine block and the heater radiator by passing coolant through the two vehicle elements as it heats the coolant. There is no provision, however, for automatically transferring heat to the enclosed area. In U.S. Pat. No. 4,398,081 issued Aug. 9, 1983 to Mark H. Moad, an electric heating element and pump are connected in series in the coolant line to circulate the heated coolant first through the heater radiator, providing the hottest fluid there, and then the engine. A switch circuit is provided which turns on the heater blower when the electric heating element is on.
The above and similar devices are limited to heating one area of the vehicle or tend to give priority to one when both are heated. Those which include heater, pump or other elements in series within the vehicle's coolant line may have a deleterious effect on engine cooling or heater operation when the engine is running. Not only may the enclosed elements resist smooth fluid flow but they themselves are subject to the flow during engine operation.